[Amps] Dual 3-1000Z amp problem

[Clark Turner]

I think we figured out the issue.  I had used 6K ohm for the plate load 
resistor and back fed the Network with a 259B in order to make a tuning 
chart.  I should have used about 3K I guess.  I set the C load around 
1000 PF, then fed 10 watts am into the amp and found the peak on the 
roller.  Then went from there.  The old 4-1000s at 10KV plate voltage 
used wildly different settings for the roller.  I found 20 to 25 uH 
worked for 80 meters. I had it set at 40uH before.

The amp now does 3000 out with 100 watts of drive on 80 meters with 
plate voltage about 4500 volts.  It makes legal limit on the air with 40 
watts drive and is very clean on the output.

Tonight, I installed and tuned the tuned input.  I got 10 to 80 less 
than 1.3 to 1 now and its band switched on front panel.

It works. Not perfectly, but it works. Probably not to many Dual 3-1000Z 
amps out there anymore so I am proud of it.


C

On 4/19/2016 12:23 PM, TexasRF at aol.com wrote:
> You are retuning the plate circuit to match the new lower plate load 
> Z, right? If you are, you might try a different watt meter.
> 73,
> Gerald K5GW
> In a message dated 4/19/2016 2:17:45 P.M. Central Daylight Time, 
> Clark at ClarkTurnerTuning.com writes:
>
>     I just finished my Dual 3-1000Z GG amplifier.  I have an odd issue
>     now
>     that I cant seem to figure out. The amp will do 2KW with 40 watts of
>     drive on 80 meters.  Additional drive does not add any power out. 
>     100
>     watts input does 2kW out.  The Input SWR is low at 1.2 to 1.  The
>     plate
>     current DOES increase, But there is no additional output.
>
>     I had this amp running before with 4-1000 and 3-1000s and some of you
>     remember, I turned the roller inductor on accident when I was
>     trying to
>     reach for the load turns counter. That toasted the plate choke. I
>     replaced that choke and while I was in the amp, I installed RF parts
>     RFC30 chokes instead of the HB ones.  I was having high input on
>     80 so I
>     changed them out. That is fixed but I now have this new issue.
>
>     Any idea where to go?  This condition exists on 40 and 80.  2KW easy.
>     But then it wont make more.
>
>     C
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